fs: implement copyFileSync in C++

[anonrig]

Move fs.copyFileSync() path validation, file URL conversion, NUL
checks, mode validation, permission-model checks, and the copy into a
dedicated C++ binding.

JavaScript only does VFS dispatch (still before validation). The copy
itself uses uv_fs_copyfile, so COPYFILE_EXCL / FICLONE /
FICLONE_FORCE, mode/timestamp preservation, and UV error shapes
(syscall: 'copyfile', path / dest) stay the same.

This also fixes a crash in the C++ FileURLToPath helper:
ERR_INVALID_FILE_URL_HOST used a format string without %s, which
aborted on file URLs with a hostname. That path is now reachable from
copyFileSync.

Performance

Same-binary comparison of the old JS getValidatedPath +
binding.copyFile path vs binding.copyFileSync (n=10000):

case	old	C++	change
valid copy	64.7 µs/op	60.6 µs/op	~6% faster
missing src (ENOENT)	4.64 µs/op	4.29 µs/op	~7% faster
invalid type	8.31 µs/op	2.68 µs/op	~68% faster
file URL	61.0 µs/op	60.3 µs/op	~1% faster

benchmark/fs/bench-copyFileSync.js (n=10000) is dominated by
uv_fs_copyfile I/O on valid and by ENOENT on invalid; those
cases stay within a few percent of the old path.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Tests

• test/parallel/test-fs-copyfile.js (Buffer, Uint8Array, file: URL, non-file URL, encoded slashes, file URL host)
• test/parallel/test-fs-copyfile-respect-permissions.js
• test/parallel/test-fs-null-bytes.js
• test/parallel/test-fs-error-messages.js
• test/parallel/test-permission-fs-read.js / test-permission-fs-write.js
• VFS copyFileSync tests

[nodejs-github-bot]

Review requested:

• @nodejs/url

[codecov]

Codecov Report

❌ Patch coverage is 72.56637% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.12%. Comparing base (cf30b2e) to head (e4dc3a1).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_file.cc	72.07%	10 Missing and 21 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65376      +/-   ##
==========================================
+ Coverage   90.11%   90.12%   +0.01%     
==========================================
  Files         752      752              
  Lines      251861   251968     +107     
  Branches    47365    47396      +31     
==========================================
+ Hits       226955   227082     +127     
+ Misses      16238    16203      -35     
- Partials     8668     8683      +15     

Files with missing lines	Coverage Δ
lib/fs.js	98.36% <100.00%> (-0.01%)	⬇️
src/node_url.cc	80.97% <100.00%> (+3.26%)	⬆️
src/node_file.cc	73.96% <72.07%> (-0.27%)	⬇️

... and 32 files with indirect coverage changes

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